There are a number of reasons for the crash of pollinator bees worldwide. Mainly, those are habitat loss (nearly 40% of all land is used for agriculture, according to the Food and Agriculture Organization), climate change (the land that's left is changing, and this is shrinking the ranges of some bees) and rampant chemical use.

"The rusty patched bumblebee is among a group of pollinators, including the monarch butterfly, experiencing serious declines across the country," Melius said. "Why is this important? Pollinators are small but mighty parts of the natural mechanism that sustains us and our world. Without them ... our crops require laborious, costly pollination by hand."

The species joins seven species of yellow-faced bees found in Hawaii on the endangered list. It is one of 47 bumblebee species in North America.

Photos:The amazing diversity of wild bees

Photos:The amazing diversity of wild bees

There are an estimated 20,000 bee species worldwide, including those with green and blue bodies. This bee was collected from Biscayne National Park near Miami.

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Photos:The amazing diversity of wild bees

"An obscure bee of the desert, Martinapis luteicornis, only is active early in the morning just as the sky begins to lighten," writes Sam Droege with the US Geological Survey.

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Photos:The amazing diversity of wild bees

This male bee comes from Oahu, Hawaii.

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Photos:The amazing diversity of wild bees

"Ah, the lovely yellow of Bombus perplexus," writes Droege. "For some reason, this species' coloration tends towards bright yellow while other eastern bumbles are more subdued in their yellowness. It varies with their age (the sun fade bumbles plumage) but a nice lemon yellow (color) usually means this species."

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Photos:The amazing diversity of wild bees

Anthidiellum ehrhorni lives in the dry, US Southwest.

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Photos:The amazing diversity of wild bees

This bee with iridescent wings was collected in Michigan.

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Photos:The amazing diversity of wild bees

This bombus perplexus -- a bumblebee -- specimen is from central Pennsylvania.

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Photos:The amazing diversity of wild bees

Andrena wellesleyana is "one of a number of species where the males have extensive yellow on their faces while the females are completely black."

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Photos:The amazing diversity of wild bees

A bee captured in Arizona. It has orange pollen stuck to its face and sides.

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Photos:The amazing diversity of wild bees

Diadasia rinconis, a bee with pollen and "a few stray cactus balls" on its hairy body, writes Droege.

Bombus ternarius -- a bumblebee -- was collected in Franklin County, New York. "In most of New England, the only Bumble Bee with significant orange and yellow on its abdomen," Droege writes.

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Photos:The amazing diversity of wild bees

Bombus bimaculatus is another species of bumblebee, found in Virginia.

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Sarina Jepsen, deputy chair of the International Union for Conservation of Nature's bumblebee specialist group, and a director at the Xerces Society, an environmental nonprofit, told CNN in December that about 25% of bumblebees in North America are at risk for extinction.

On Tuesday, she commended the wildlife service's decision.

"Now that the Fish & Wildlife Service has listed the rusty patched bumblebee as endangered, it stands a chance of surviving the many threats it faces," she said.

There are roughly 20,000 species of bees in the world. That's more species than birds, amphibians, reptiles or mammals.

Bumblebees live in underground colonies, caring for a queen. Worker bees -- females that don't reproduce because they're not the queen -- fly around during the day collecting flower pollen and nectar for food and energy.

They only live for a year, except the queen who is dormant during the winter and emerges in the spring to begin a new colony with eggs fertilized during the prior fall.